Band-pass filter

ABSTRACT

A band-pass filter includes five resonators. The five resonators are configured so that capacitive coupling is established between every two of the resonators adjacent to each other in circuit configuration. The first stage resonator and the fifth stage resonator are magnetically coupled to each other. The second stage resonator and the fourth stage resonator are capacitively coupled to each other. Each of the five resonators includes a resonator conductor portion. The respective resonator conductor portions of the first and fifth stage resonators are physically adjacent to each other. The respective resonator conductor portions of the second and fourth stage resonators are physically adjacent to each other. The respective resonator conductor portions of the first and second stage resonators are physically adjacent to each other. The respective resonator conductor portions of the fourth and fifth stage resonators are physically adjacent to each other.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a band-pass filter including aplurality of resonators.

2. Description of the Related Art

The standardization of fifth-generation mobile communication systems(hereinafter referred to as 5G) is currently ongoing. For 5G, the use offrequency bands of 10 GHz or higher, particularly a quasi-millimeterwave band of 10 to 30 GHz and a millimeter wave band of 30 to 300 GHz,is being studied to expand the frequency band.

One of electronic components used in a communication apparatus is aband-pass filter including a plurality of resonators. Each of theplurality of resonators includes, for example, a conductor portion thatis long in one direction.

JP2006-311100A describes a chip-type multistage filter device usable inquasi-millimeter and millimeter wave bands. The chip-type multistagefilter device includes a multilayer substrate, first and second surfaceground electrodes, first and second internal ground electrodes, andfirst and second λ/2 resonator electrodes. The multilayer substrate isformed by stacking a plurality of dielectric layers. The multilayersubstrate has first and second main surfaces opposed to each other, andfirst to fourth side surfaces connecting the first and second mainsurfaces. The first side surface and the second side surface are opposedto each other. The first surface ground electrode is disposed on thefirst side surface. The second surface ground electrode is disposed onthe second side surface. The first internal ground electrode is disposedon one of the dielectric layers of the multilayer substrate that isrelatively close to the first main surface. The second internal groundelectrode is disposed on another one of the dielectric layers of themultilayer substrate that is relatively close to the second mainsurface. The first and second λ/2 resonator electrodes are disposed inan area surrounded by the first and second surface ground electrodes andthe first and second internal ground electrodes.

The chip-type multistage filter device described in JP2006-311100Afurther includes a via hole conductor and a capacitance unit. The viahole conductor is formed to run through at least some of the dielectriclayers so that the first and second internal ground electrodes areelectrically connected to each other. The first and second λ/2 resonatorelectrodes are opposed to each other with the via hole conductorinterposed therebetween. The capacitance unit is disposed within themultilayer substrate to add a coupling capacitance to between the firstand second λ/2 resonator electrodes.

One of favorable characteristics of the band-pass filters is a steepchange in insertion loss in at least one of two frequency regions: afirst passband-vicinity region and a second passband-vicinity region,the first passband-vicinity region being a frequency region close to thepassband and lower than the passband, the second passband-vicinityregion being a frequency region close to the passband and higher thanthe passband. Such a characteristic can be achieved by, for example,creating an attenuation pole in at least one of the first and secondpassband-vicinity regions in the frequency response of the insertionloss.

“Basics and Design of Practical Microwave Filer”, first edition, writtenby Yoshihiro Konishi, published by K-Laboratory in October 2009describes, at page 131, line 1 to page 132, line 4, and FIGS. 3.81 and3.82, a method for producing traps at a lower frequency than a passbandand a higher frequency than the passband by providing two multipaths(also referred to as cross couplings) in a six-stage band-pass filterhaving six resonators in which every two of the resonators adjacent toeach other in circuit configuration are configured to beelectromagnetically coupled to each other.

The document of Konishi describes the circuit configuration of thesix-stage band-pass filter having the two multipaths, but does notdescribe physical structure. When the band-pass filter is embodied as anactual electronic component, directly replacing the circuitconfiguration described in the document of Konishi with physicalstructure may cause the electronic component to have an increased sizeor a complicated structure.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a band-pass filterthat has two cross couplings and is simple in structure.

A band-pass filter of the present invention includes: a main body formedof a dielectric; a first input/output port and a second input/outputport integrated with the main body; and five or more resonators. Thefive or more resonators are provided within the main body, locatedbetween the first input/output port and the second input/output port incircuit configuration, and configured so that electromagnetic couplingis established between every two of the resonators adjacent to eachother in circuit configuration.

Each of the five or more resonators includes a resonator conductorportion formed of a conductor. The five or more resonators include: afirst resonator and a second resonator that are configured to bemagnetically coupled to each other although not adjacent to each otherin circuit configuration; and a third resonator and a fourth resonatorthat are configured to be capacitively coupled to each other althoughnot adjacent to each other in circuit configuration. The first resonatorand the third resonator are adjacent to each other in circuitconfiguration. The second resonator and the fourth resonator areadjacent to each other in circuit configuration. The resonator conductorportion of the first resonator and the resonator conductor portion ofthe second resonator are physically adjacent to each other without anyresonator conductor portion of another resonator therebetween. Theresonator conductor portion of the third resonator and the resonatorconductor portion of the fourth resonator are physically adjacent toeach other without any resonator conductor portion of another resonatortherebetween. The resonator conductor portion of the first resonator andthe resonator conductor portion of the third resonator are physicallyadjacent to each other without any resonator conductor portion ofanother resonator therebetween. The resonator conductor portion of thesecond resonator and the resonator conductor portion of the fourthresonator are physically adjacent to each other without any resonatorconductor portion of another resonator therebetween.

In the band-pass filter of the present invention, the electromagneticcoupling between every two of the resonators adjacent to each other incircuit configuration may be capacitive coupling.

In the band-pass filter of the present invention, each of the five ormore resonators may be a resonator with open ends.

In the band-pass filter of the present invention, the five or moreresonators may be five resonators. In this case, the first resonator maybe a resonator that is the closest to the first input/output port incircuit configuration, and the second resonator may be a resonator thatis the closest to the second input/output port in circuit configuration.The third resonator may be a resonator that is the second closest to thefirst input/output port in circuit configuration, and the fourthresonator may be a resonator that is the second closest to the secondinput/output port in circuit configuration.

In the band-pass filter of the present invention, the five or moreresonators may be six resonators. In this case, the first resonator maybe a resonator that is the second closest to the first input/output portin circuit configuration, and the second resonator may be a resonatorthat is the second closest to the second input/output port in circuitconfiguration. The third resonator may be a resonator that is theclosest to the first input/output port in circuit configuration, and thefourth resonator may be a resonator that is the closest to the secondinput/output port in circuit configuration.

The band-pass filter of the present invention may further include anotch filter section for attenuating a signal of a predeterminedfrequency higher than the passband.

In the band-pass filter of the present invention, the main body mayinclude a multilayer stack composed of a plurality of dielectric layersstacked together. In this case, the respective resonator conductorportions of the first to fourth resonators may be located at the sameposition in the multilayer stack in a direction in which the pluralityof dielectric layers are stacked.

The band-pass filter of the present invention may further include ashield and a partition. The shield is formed of a conductor andintegrated with the main body. The partition is formed of a conductor,provided within the main body, and electrically connected to the shield.The shield includes a first portion and a second portion spaced fromeach other in a first direction, and a connecting portion connecting thefirst and second portions. The first portion, the second portion and theconnecting portion are arranged to surround the five or more resonators.The resonator conductor portion of each of the five or more resonatorsextends in a direction intersecting the first direction. The partitionis in contact with the first portion and the second portion. At leastpart of the partition extends to pass between the resonator conductorportion of the first resonator and the resonator conductor portion ofthe second resonator.

When the band-pass filter of the present invention includes the shieldand the partition, the main body may include a multilayer stack composedof a plurality of dielectric layers stacked together in the firstdirection. In such a case, the multilayer stack may include a mainportion composed of two or more dielectric layers stacked together,among the plurality of dielectric layers. The main portion has a firstend face and a second end face located at opposite ends in the firstdirection. The first portion may be formed of a first conductor layerdisposed on the first end face. The second portion may be formed of asecond conductor layer disposed on the second end face. The partitionmay run through the two or more dielectric layers. The partition mayinclude a plurality of first through hole lines each running through thetwo or more dielectric layers. Each of the plurality of first throughhole lines may include two or more through holes connected in series.The connecting portion of the shield may include a plurality of secondthrough hole lines each running through the two or more dielectriclayers. Each of the plurality of second through hole lines may includetwo or more through holes connected in series.

In the band-pass filter of the present invention, the first to fourthresonators and their respective resonator conductor portions areconfigured to have the above-described relationship. The presentinvention thus realizes a band-pass filter that has two cross couplingsand is simple in structure.

Other and further objects, features and advantages of the invention willappear more fully from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view illustrating the structure of a band-passfilter according to a first embodiment of the invention.

FIG. 2 is a circuit diagram illustrating the circuit configuration ofthe band-pass filter according to the first embodiment of the invention.

FIG. 3 is an explanatory diagram illustrating a patterned surface of afirst dielectric layer of a multilayer stack shown in FIG. 1.

FIG. 4 is an explanatory diagram illustrating a patterned surface of asecond dielectric layer of the multilayer stack shown in FIG. 1.

FIG. 5 is an explanatory diagram illustrating a patterned surface of athird dielectric layer of the multilayer stack shown in FIG. 1.

FIG. 6 is an explanatory diagram illustrating a patterned surface of afourth dielectric layer of the multilayer stack shown in FIG. 1.

FIG. 7 is an explanatory diagram illustrating a patterned surface ofeach of a fifth to a seventh dielectric layer of the multilayer stackshown in FIG. 1.

FIG. 8 is an explanatory diagram illustrating a patterned surface of aneighth dielectric layer of the multilayer stack shown in FIG. 1.

FIG. 9 is an explanatory diagram illustrating a patterned surface of aninth dielectric layer of the multilayer stack shown in FIG. 1.

FIG. 10 is an explanatory diagram illustrating a patterned surface ofeach of a tenth to a seventeenth dielectric layer of the multilayerstack shown in FIG. 1.

FIG. 11 is an explanatory diagram illustrating a patterned surface of aneighteenth dielectric layer of the multilayer stack shown in FIG. 1.

FIG. 12 is a characteristic diagram illustrating an example of thefrequency response of the insertion loss of the band-pass filteraccording to the first embodiment of the invention.

FIG. 13 is a characteristic diagram illustrating an example of thefrequency response of the insertion loss of a band-pass filter of afirst comparative example.

FIG. 14 is a perspective view illustrating the structure of a band-passfilter according to a second embodiment of the invention.

FIG. 15 is a circuit diagram illustrating the circuit configuration ofthe band-pass filter according to the second embodiment of theinvention.

FIG. 16 is an explanatory diagram illustrating a patterned surface of afirst dielectric layer of the multilayer stack shown in FIG. 14.

FIG. 17 is an explanatory diagram illustrating a patterned surface ofeach of a second and a third dielectric layer of the multilayer stackshown in FIG. 14.

FIG. 18 is an explanatory diagram illustrating a patterned surface of afourth dielectric layer of the multilayer stack shown in FIG. 14.

FIG. 19 is an explanatory diagram illustrating a patterned surface ofeach of a fifth to a ninth dielectric layer of the multilayer stackshown in FIG. 14.

FIG. 20 is an explanatory diagram illustrating a patterned surface of atenth dielectric layer of the multilayer stack shown in FIG. 14.

FIG. 21 is an explanatory diagram illustrating a patterned surface of aneleventh dielectric layer of the multilayer stack shown in FIG. 14.

FIG. 22 is an explanatory diagram illustrating a patterned surface of atwelfth dielectric layer of the multilayer stack shown in FIG. 14.

FIG. 23 is an explanatory diagram illustrating a patterned surface ofeach of a thirteenth to a twenty-first dielectric layer of themultilayer stack shown in FIG. 14.

FIG. 24 is an explanatory diagram illustrating a patterned surface of atwenty-second dielectric layer of the multilayer stack shown in FIG. 14.

FIG. 25 is a characteristic diagram illustrating an example of thefrequency response of the insertion loss of the band-pass filteraccording to the second embodiment of the invention.

FIG. 26 is a characteristic diagram illustrating an example of thefrequency response of the insertion loss of a band-pass filter of asecond comparative example.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

Preferred embodiments of the present invention will now be described indetail with reference to the drawings. First, reference is made to FIG.1 and FIG. 2 to describe the configuration of a band-pass filteraccording to a first embodiment of the invention. FIG. 1 is aperspective view illustrating the structure of the band-pass filteraccording to the present embodiment. FIG. 2 is a circuit diagramillustrating the circuit configuration of the band-pass filter accordingto the present embodiment.

As shown in FIG. 1, the band-pass filter 1 according to the presentembodiment includes: a main body 2 formed of a dielectric; a firstinput/output port 3 and a second input/output port 4 integrated with themain body 2; five or more resonators provided within the main body 2; ashield 6; a first partition 7; and a second partition 8. The shield 6 isformed of a conductor and integrated with the main body 2. The shield 6is connected to the ground. The shield 6 has the function of preventingelectromagnetic radiation to the surroundings of the band-pass filter 1.Each of the first partition 7 and the second partition 8 is formed of aconductor, provided within the main body 2 and electrically connected tothe shield 6. The first partition 7 corresponds to the partition in thepresent invention.

The main body 2 includes a multilayer stack 20 composed of a pluralityof dielectric layers stacked together. Here, X, Y and Z directions aredefined as shown in FIG. 1. The X, Y and Z directions are orthogonal toone another. In the present embodiment, the direction in which theplurality of dielectric layers are stacked is the Z direction (theupward direction in FIG. 1). The Z direction corresponds to the firstdirection in the present invention.

The main body 2 is shaped like a rectangular solid. The main body 2 hasa first end face 2A and a second end face 2B located at opposite ends inthe Z direction of the main body 2, and further has four side surfaces2C, 2D, 2E and 2F connecting the first end face 2A and the second endface 2B. The first end face 2A is also the bottom surface of the mainbody 2. The second end face 2B is also the top surface of the main body2. The side surfaces 2C and 2D are located at opposite ends in the Ydirection of the main body 2. The side surfaces 2E and 2F are located atopposite ends in the X direction of the main body 2.

The five or more resonators are located between the first input/outputport 3 and the second input/output port 4 in circuit configuration. Thefive or more resonators are configured so that electromagnetic couplingis established between every two of the resonators adjacent to eachother in circuit configuration. As used herein, the phrase “in circuitconfiguration” is to describe layout in a circuit diagram, not in aphysical configuration. Among the five or more resonators, a resonatorthat is the n-th closest to the first input/output port 3 in circuitconfiguration may also be referred to as the n-th stage resonator.

In the present embodiment, as shown in FIG. 2, the five or moreresonators are specifically five resonators 51, 52, 53, 54 and 55. Thefive resonators 51, 52, 53, 54 and 55 are arranged in this order, fromclosest to farthest, from the first input/output port 3 in circuitconfiguration. The resonators 51 to 55 are configured so that theresonators 51 and 52 are adjacent to each other in circuit configurationand are electromagnetically coupled to each other, the resonators 52 and53 are adjacent to each other in circuit configuration and areelectromagnetically coupled to each other, the resonators 53 and 54 areadjacent to each other in circuit configuration and areelectromagnetically coupled to each other, and the resonators 54 and 55are adjacent to each other in circuit configuration and areelectromagnetically coupled to each other. In the present embodiment,the electromagnetic coupling between every two of the resonatorsadjacent to each other in circuit configuration is specificallycapacitive coupling. In the present embodiment, each of the resonators51 to 55 is a resonator with open ends, and also a half-wave resonator.

The band-pass filter 1 includes a capacitor C12 for establishingcapacitive coupling between the resonators 51 and 52, a capacitor C23for establishing capacitive coupling between the resonators 52 and 53, acapacitor C34 for establishing capacitive coupling between theresonators 53 and 54, and a capacitor C45 for establishing capacitivecoupling between the resonators 54 and 55.

In a band-pass filter including three or more resonators configured sothat every two of the resonators adjacent to each other in circuitconfiguration are coupled to each other, electromagnetic coupling may beestablished between two resonators that are not adjacent to each otherin circuit configuration. Such electromagnetic coupling betweennon-adjacent resonators will be referred to as cross coupling. As willbe described in detail below, the band-pass filter 1 according to thepresent embodiment has two cross couplings.

In the present embodiment, among the five resonators 51 to 55, theresonator 51, which is the closest to the first input/output port 3 incircuit configuration, and the resonator 55, which is the closest to thesecond input/output port 4 in circuit configuration, are magneticallycoupled to each other although they are not adjacent to each other incircuit configuration. The resonator 51 corresponds to the firstresonator in the present invention. The resonator 55 corresponds to thesecond resonator in the present invention.

Further, in the present embodiment, among the five resonators 51 to 55,the resonator 52, which is the second closest to the first input/outputport 3 in circuit configuration, and the resonator 54, which is thesecond closest to the second input/output port 4 in circuitconfiguration, are capacitively coupled to each other although they arenot adjacent to each other in circuit configuration. The resonator 52corresponds to the third resonator in the present invention. Theresonator 54 corresponds to the fourth resonator in the presentinvention. In FIG. 2, the capacitor symbol C24 represents the capacitivecoupling between the resonators 52 and 54. The band-pass filter 1further includes a capacitor C1 provided between the first input/outputport 3 and the resonator 51, and a capacitor C2 provided between thesecond input/output port 4 and the resonator 55.

The band-pass filter 1 further includes a notch filter section forattenuating a signal of a predetermined frequency (hereinafter referredto as notch frequency) higher than the passband. The notch filtersection includes two lines 91 and 92 each formed of a conductor. Each ofthe lines 91 and 92 has a first end and a second end opposite to eachother. The first end of the line 91 is connected to the firstinput/output port 3, and the second end of the line 91 is open. Thefirst end of the line 92 is connected to the second input/output port 4,and the second end of the line 92 is open. Each of the lines 91 and 92has a length of one quarter or nearly one quarter the wavelengthcorresponding to the notch frequency. Each of the lines 91 and 92 is aquarter-wave resonator that resonates at the notch frequency. The notchfrequency is, for example, twice the center frequency of the passband ofthe band-pass filter 1.

The shield 6 includes a first portion 61 and a second portion 62 spacedfrom each other in the first direction, i.e., the Z direction, and aconnecting portion 63 connecting the first portion 61 and the secondportion 62. The first portion 61, the second portion 62 and theconnecting portion 63 are arranged to surround the five resonators 51 to55.

The multilayer stack 20 includes a main portion 21 and a coating portion22. The main portion 21 is composed of two or more dielectric layersstacked together, among the plurality of dielectric layers constitutingthe multilayer stack 20. The coating portion 22 is composed of one ormore dielectric layers other than the two or more dielectric layersconstituting the main portion 21, among the plurality of dielectriclayers constituting the multilayer stack 20. The main portion 21 has afirst end face 21 a and a second end face 21 b located at opposite endsin the direction in which the two or more dielectric layers are stacked.The coating portion 22 covers the second end face 21 b. The first endface 21 a of the main portion 21 coincides with the first end face 2A ofthe main body 2. The second end face 21 b of the main portion 21 islocated within the main body 2.

The first portion 61 is formed of a first conductor layer 313 disposedon the first end face 21 a. The second portion 62 is formed of a secondconductor layer 481 disposed on the second end face 21 b. The secondportion 62 is interposed between the main portion 21 and the coatingportion 22.

The resonator 51 includes a resonator conductor portion 510 formed of aconductor. The resonator 52 includes a resonator conductor portion 520formed of a conductor. The resonator 53 includes a resonator conductorportion 530 formed of a conductor. The resonator 54 includes a resonatorconductor portion 540 formed of a conductor. The resonator 55 includes aresonator conductor portion 550 formed of a conductor.

Each of the resonator conductor portions 510, 520, 530, 540 and 550extends in a direction intersecting the first direction or the Zdirection. In the present embodiment, specifically, each of theresonator conductor portions 510, 520, 530, 540 and 550 extends in adirection orthogonal to the first direction or the Z direction.

Each of the resonator conductor portions 510, 520, 530, 540 and 550 hasa first end and a second end opposite to each other. As mentioned above,each of the resonators 51 to 55 is a resonator with open ends. Thus,both of the first and second ends of each of the resonator conductorportions 510, 520, 530, 540 and 550 are open. Each of the resonatorconductor portions 510, 520, 530, 540 and 550 has a length of one halfor nearly one half the wavelength corresponding to the center frequencyof the passband of the band-pass filter 1.

The first partition 7 is in contact with the first portion 61 and thesecond portion 62. At least part of the first partition 7 extends topass between the resonator conductor portion 510 and the resonatorconductor portion 550. In the present embodiment, specifically, thefirst partition 7 extends in the first direction, i.e., the Z direction.The first partition 7 connects the first portion 61 and the secondportion 62 via the shortest path. To be more specific, the length of thefirst partition 7 in the Z direction is equal to the distance betweenthe first portion 61 and the second portion 62.

The first partition 7 runs through the two or more dielectric layersconstituting the main portion 21. In the present embodiment, the firstpartition 7 includes a plurality of through hole lines 7T each runningthrough the two or more dielectric layers constituting the main portion21. The plurality of through hole lines 7T correspond to the pluralityof first through hole lines in the present invention. In FIG. 1, eachthrough hole line 7T is represented by a circular column. Each of thethrough hole lines 7T includes two or more through holes connected inseries. Each of the through hole lines 7T extends in the Z direction.The through hole lines 7T are arranged to be adjacent to each other inthe Y direction. In the present embodiment, the number of the throughhole lines 7T is five.

The second partition 8 extends to pass through the area surrounded bythe resonator conductor portions 520, 530 and 540, and is in contactwith the first portion 61 and the second portion 62. In the presentembodiment, specifically, the second partition 8 extends in the firstdirection, i.e., the Z direction. The second partition 8 connects thefirst portion 61 and the second portion 62 via the shortest path. To bemore specific, the length of the second partition 8 in the Z directionis equal to the distance between the first portion 61 and the secondportion 62.

The second partition 8 runs through the two or more dielectric layersconstituting the main portion 21. In the present embodiment, the secondpartition 8 includes a plurality of through hole lines 8T each runningthrough the two or more dielectric layers constituting the main portion21. In FIG. 1, each through hole line 8T is represented by a circularcolumn. Each of the through hole lines 8T includes two or more throughholes connected in series. Each of the through hole lines 8T extends inthe Z direction. The through hole lines 8T are arranged to be adjacentto each other in the X direction. In the present embodiment, the numberof the through hole lines 8T is five.

The connecting portion 63 of the shield 6 includes a plurality ofthrough hole lines 63T each running through the two or more dielectriclayers constituting the main portion 21. The plurality of through holelines 63T correspond to the second through hole lines in the presentinvention. In FIG. 1, each through hole line 63T is represented by acircular column. All the through hole lines represented by circularcolumns in FIG. 1, except the five through hole lines 7T and the fivethrough hole lines 8T, are the through hole lines 63T. Each of thethrough hole lines 63T includes two or more through holes connected inseries. Each of the through hole lines 63T extends in the Z direction.

Reference is now made to FIG. 3 to FIG. 11 to describe an example of thedielectric layers constituting the multilayer stack 20 and theconfiguration of a plurality of conductor layers formed on thedielectric layers and a plurality of through holes formed in thedielectric layers. In this example, the multilayer stack 20 includeseighteen dielectric layers stacked together. The eighteen dielectriclayers will be referred to as the first to eighteenth dielectric layersin the order from bottom to top. The first to eighteenth dielectriclayers are denoted by reference numerals 31 to 48, respectively. Themain portion 21 is composed of the first to seventeenth dielectriclayers 31 to 47. The coating portion 22 is composed of the eighteenthdielectric layer 48. In FIG. 3 to FIG. 10, each circle represents athrough hole.

FIG. 3 illustrates a patterned surface of the first dielectric layer 31.On the patterned surface of the first dielectric layer 31, there areformed a conductor layer 311 forming the first input/output port 3, aconductor layer 312 forming the second input/output port 4, and thefirst conductor layer 313 forming the first portion 61 of the shield 6.

Further, a through hole 31T1 connected to the conductor layer 311, and athrough hole 31T2 connected to the conductor layer 312 are formed in thedielectric layer 31. Further formed in the dielectric layer 31 are fivethrough holes 7T1 constituting respective portions of the five throughhole lines 7T, five through holes 8T1 constituting respective portionsof the five through hole lines 8T, and a plurality of through holes 63T1constituting respective portions of the plurality of through hole lines63T. All the through holes represented by circles in FIG. 3, except thethrough holes 31T1, 31T2, 7T1 and 8T1, are the through holes 63T1. Thethrough holes 7T1, 8T1 and 63T1 are connected to the first conductorlayer 313.

FIG. 4 illustrates a patterned surface of the second dielectric layer32. Conductor layers 321 and 322 are formed on the patterned surface ofthe dielectric layer 32. The through holes 31T1 and 31T2 shown in FIG. 3are connected to the conductor layers 321 and 322, respectively.

In the dielectric layer 32, there are formed a through hole 32T1connected to the conductor layer 321, and a through hole 32T2 connectedto the conductor layer 322.

Further formed in the dielectric layer 32 are five through holes 7T2constituting respective portions of the five through hole lines 7T. Thefive through holes 7T1 shown in FIG. 3 are connected to the five throughholes 7T2, respectively.

Further formed in the dielectric layer 32 are five through holes 8T2constituting respective portions of the five through hole lines 8T. Thefive through holes 8T1 shown in FIG. 3 are connected to the five throughholes 8T2, respectively.

Further formed in the dielectric layer 32 are a plurality of throughholes 63T2 constituting respective portions of the plurality of throughhole lines 63T. All the through holes represented by circles in FIG. 4,except the through holes 32T1, 32T2, 7T2 and 8T2, are the through holes63T2. The plurality of through holes 63T1 shown in FIG. 3 are connectedto the plurality of through holes 63T2, respectively.

FIG. 5 illustrates a patterned surface of the third dielectric layer 33.Through holes 33T1 and 33T2 are formed in the dielectric layer 33. Thethrough holes 32T1 and 32T2 shown in FIG. 4 are connected to the throughholes 33T1 and 33T2, respectively.

Further formed in the dielectric layer 33 are five through holes 7T3constituting respective portions of the five through hole lines 7T. Thefive through holes 7T2 shown in FIG. 4 are connected to the five throughholes 7T3, respectively.

Further formed in the dielectric layer 33 are five through holes 8T3constituting respective portions of the five through hole lines 8T. Thefive through holes 8T2 shown in FIG. 4 are connected to the five throughholes 8T3, respectively.

Further formed in the dielectric layer 33 are a plurality of throughholes 63T3 constituting respective portions of the plurality of throughhole lines 63T. All the through holes represented by circles in FIG. 5,except the through holes 33T1, 33T2, 7T3 and 8T3, are the through holes63T3. The plurality of through holes 63T2 shown in FIG. 4 are connectedto the plurality of through holes 63T3, respectively.

FIG. 6 illustrates a patterned surface of the fourth dielectric layer34. On the patterned surface of the dielectric layer 34, there areformed a conductor layer 341 forming the line 91, and a conductor layer342 forming the line 92. Each of the conductor layers 341 and 342 has afirst end and a second end opposite to each other. The through hole 33T1shown in FIG. 5 is connected to a portion of the conductor layer 341near the first end thereof. The through hole 33T2 shown in FIG. 5 isconnected to a portion of the conductor layer 342 near the first endthereof. A portion of the conductor layer 341 near the second endthereof and a portion of the conductor layer 342 near the second endthereof are opposed to the conductor layer 313 shown in FIG. 3 with thedielectric layers 31, 32 and 33 interposed between the conductor layer313 and each of the aforementioned portions of the conductor layers 341and 342.

Further formed in the dielectric layer 34 are a through hole 34T1connected to the portion of the conductor layer 341 near the first endthereof, and a through hole 34T2 connected to the portion of theconductor layer 342 near the first end thereof.

Further formed in the dielectric layer 34 are five through holes 7T4constituting respective portions of the five through hole lines 7T. Thefive through holes 7T3 shown in FIG. 5 are connected to the five throughholes 7T4, respectively.

Further formed in the dielectric layer 34 are five through holes 8T4constituting respective portions of the five through hole lines 8T. Thefive through holes 8T3 shown in FIG. 5 are connected to the five throughholes 8T4, respectively.

Further formed in the dielectric layer 34 are a plurality of throughholes 63T4 constituting respective portions of the plurality of throughhole lines 63T. All the through holes represented by circles in FIG. 6,except the through holes 34T1, 34T2, 7T4 and 8T4, are the through holes63T4. The plurality of through holes 63T3 shown in FIG. 5 are connectedto the plurality of through holes 63T4, respectively.

FIG. 7 illustrates a patterned surface of each of the fifth to seventhdielectric layers 35 to 37. Through holes 35T1 and 35T2 are formed ineach of the dielectric layers 35 to 37. The through holes 34T1 and 34T2shown in FIG. 6 are respectively connected to the through holes 35T1 and35T2 formed in the fifth dielectric layer 35.

In each of the dielectric layers 35 to 37, there are further formed fivethrough holes 7T5 constituting respective portions of the five throughhole lines 7T. The five through holes 7T4 shown in FIG. 6 arerespectively connected to the five through holes 7T5 formed in the fifthdielectric layer 35.

In each of the dielectric layers 35 to 37, there are further formed fivethrough holes 8T5 constituting respective portions of the five throughhole lines 8T. The five through holes 8T4 shown in FIG. 6 arerespectively connected to the five through holes 8T5 formed in the fifthdielectric layer 35.

Further, a plurality of through holes 63T5 constituting respectiveportions of the plurality of through hole lines 63T are formed in eachof the dielectric layers 35 to 37. All the through holes represented bycircles in FIG. 7, except the through holes 35T1, 35T2, 7T5 and 8T5, arethe through holes 63T5. The plurality of through holes 63T4 shown inFIG. 6 are respectively connected to the plurality of through holes 63T5formed in the fifth dielectric layer 35.

In the dielectric layers 35 to 37, every vertically adjacent throughholes denoted by the same reference signs are connected to each other.

FIG. 8 illustrates a patterned surface of the eighth dielectric layer38. On the patterned surface of the dielectric layer 38, there areformed a conductor layer 381 for forming the capacitor C1 shown in FIG.2 and a conductor layer 382 for forming the capacitor C2 shown in FIG.2. The through hole 35T1 formed in the seventh dielectric layer 37 isconnected to the conductor layer 381. The through hole 35T2 formed inthe seventh dielectric layer 37 is connected to the conductor layer 382.

On the patterned surface of the dielectric layer 38, there are furtherformed conductor layers 383, 384, 385 and 386 for forming the capacitorsC12, C23, C34 and C45 shown in FIG. 2, respectively.

Further, five through holes 7T8 constituting respective portions of thefive through hole lines 7T are formed in the dielectric layer 38. Thefive through holes 7T5 formed in the seventh dielectric layer 37 areconnected to the five through holes 7T8, respectively.

Further formed in the dielectric layer 38 are five through holes 8T8constituting respective portions of the five through hole lines 8T. Thefive through holes 8T5 formed in the seventh dielectric layer 37 areconnected to the five through holes 8T8, respectively.

Further formed in the dielectric layer 38 are a plurality of throughholes 63T8 constituting respective portions of the plurality of throughhole lines 63T. All the through holes represented by circles in FIG. 8,except the through holes 7T8 and 8T8, are the through holes 63T8. Theplurality of through holes 63T5 formed in the seventh dielectric layer37 are connected to the plurality of through holes 63T8, respectively.

FIG. 9 illustrates a patterned surface of the ninth dielectric layer 39.The resonator conductor portions 510, 520, 530, 540 and 550 are formedon the patterned surface of the dielectric layer 39.

The resonator conductor portion 510 has a first end 510 a and a secondend 510 b opposite to each other. The resonator conductor portion 520has a first end 520 a and a second end 520 b opposite to each other. Theresonator conductor portion 530 has a first end 530 a and a second end530 b opposite to each other. The resonator conductor portion 540 has afirst end 540 a and a second end 540 b opposite to each other. Theresonator conductor portion 550 has a first end 550 a and a second end550 b opposite to each other.

The resonator conductor portion 510 includes a first portion 510A, asecond portion 510B and a third portion 510C. The first portion 510Aincludes the first end 510 a, and the second portion 510B includes thesecond end 510 b. The first portion 510A extends in the X direction, andthe second portion 510B extends in the Y direction. The third portion510C connects an end of the first portion 510A opposite from the firstend 510 a and an end of the second portion 510B opposite from the secondend 510 b. In FIG. 9, the boundary between the first portion 510A andthe third portion 510C and the boundary between the second portion 510Band the third portion 510C are shown by broken lines. The first portion510A is closer to the first input/output port 3 than the second portion510B in circuit configuration.

The resonator conductor portion 550 includes a first portion 550A, asecond portion 550B and a third portion 550C. The first portion 550Aincludes the first end 550 a, and the second portion 550B includes thesecond end 550 b. The first portion 550A extends in the X direction, andthe second portion 550B extends in the Y direction. The third portion550C connects an end of the first portion 550A opposite from the firstend 550 a and an end of the second portion 550B opposite from the secondend 550 b. In FIG. 9, the boundary between the first portion 550A andthe third portion 550C and the boundary between the second portion 550Band the third portion 550C are shown by broken lines. The first portion550A is closer to the second input/output port 4 than the second portion550B in circuit configuration.

The second portion 510B of the resonator conductor portion 510 and thesecond portion 550B of the resonator conductor portion 550 are at apredetermined distance from each other and adjacent to each other in theX direction. The distance between the second portion 510B and the secondportion 550B is smaller than the length of each of the resonatorconductor portions 510 and 550.

The resonator conductor portion 520 includes a first portion 520A, asecond portion 520B and a third portion 520C. The first portion 520Aincludes the first end 520 a, and the second portion 520B includes thesecond end 520 b. The first portion 520A extends in the X direction, andthe second portion 520B extends in the Y direction. The third portion520C connects an end of the first portion 520A opposite from the firstend 520 a and an end of the second portion 520B opposite from the secondend 520 b. In FIG. 9, the boundary between the first portion 520A andthe third portion 520C and the boundary between the second portion 520Band the third portion 520C are shown by broken lines. The first end 520a is located near the second end 510 b of the resonator conductorportion 510.

The resonator conductor portion 540 includes a first portion 540A, asecond portion 540B and a third portion 540C. The first portion 540Aincludes the first end 540 a, and the second portion 540B includes thesecond end 540 b. The first portion 540A extends in the X direction, andthe second portion 540B extends in the Y direction. The third portion540C connects an end of the first portion 540A opposite from the firstend 540 a and an end of the second portion 540B opposite from the secondend 540 b. In FIG. 9, the boundary between the first portion 540A andthe third portion 540C and the boundary between the second portion 540Band the third portion 540C are shown by broken lines. The first end 540a is located near the second end 550 b of the resonator conductorportion 550.

The first end 520 a of the resonator conductor portion 520 and the firstend 540 a of the resonator conductor portion 540 are at a predetermineddistance from each other and adjacent to each other. The distancebetween the first end 520 a and the first end 540 a is sufficientlysmaller than the length of each of the resonator conductor portions 520and 540.

The resonator conductor portion 530 extends in the X direction. Thefirst end 530 a of the resonator conductor portion 530 is located nearthe second end 520 b of the resonator conductor portion 520. The secondend 530 b of the resonator conductor portion 530 is located near thesecond end 540 b of the resonator conductor portion 540.

Further, five through holes 7T9 constituting respective portions of thefive through hole lines 7T are formed in the dielectric layer 39. Thefive through holes 7T8 shown in FIG. 8 are connected to the five throughholes 7T9, respectively.

Further formed in the dielectric layer 39 are five through holes 8T9constituting respective portions of the five through hole lines 8T. Thefive through holes 8T8 shown in FIG. 8 are connected to the five throughholes 8T9, respectively.

Further formed in the dielectric layer 39 are a plurality of throughholes 63T9 constituting respective portions of the plurality of throughhole lines 63T. All the through holes represented by circles in FIG. 9,except the through holes 7T9 and 8T9, are the through holes 63T9. Theplurality of through holes 63T8 shown in FIG. 8 are connected to theplurality of through holes 63T9, respectively.

FIG. 10 illustrates a patterned surface of each of the tenth toseventeenth dielectric layers 40 to 47. Five through holes 7T10constituting respective portions of the five through hole lines 7T areformed in each of the dielectric layers 40 to 47. The five through holes7T9 shown in FIG. 9 are respectively connected to the five through holes7T10 formed in the tenth dielectric layer 40.

In each of the dielectric layers 40 to 47, there are further formed fivethrough holes 8T10 constituting respective portions of the five throughhole lines 8T. The five through holes 8T9 shown in FIG. 9 arerespectively connected to the five through holes 8T10 formed in thetenth dielectric layer 40.

Further, a plurality of through holes 63T10 constituting respectiveportions of the plurality of through hole lines 63T are formed in eachof the dielectric layers 40 to 47. All the through holes represented bycircles in FIG. 10, except the through holes 7T10 and 8T10, are thethrough holes 63T10. The plurality of through holes 63T9 shown in FIG. 9are respectively connected to the plurality of through holes 63T10formed in the tenth dielectric layer 40.

In the dielectric layers 40 to 47, every vertically adjacent throughholes denoted by the same reference signs are connected to each other.

FIG. 11 illustrates a patterned surface of the eighteenth dielectriclayer 48. The second conductor layer 481 forming the second portion 62of the shield 6 is formed on the patterned surface of the dielectriclayer 48. The through holes 7T10, 8T10 and 63T10 formed in theseventeenth dielectric layer 47 are connected to the second conductorlayer 481.

The band-pass filter 1 according to the present embodiment is formed bystacking the first to eighteenth dielectric layers 31 to 48 such thatthe patterned surface of the first dielectric layer 31 also serves asthe first end face 2A of the main body 2. A surface of the eighteenthdielectric layer 48 opposite to the patterned surface serves as thesecond end face 2B of the main body 2. The first to eighteenthdielectric layers 31 to 48 constitute the multilayer stack 20.

The respective resonator conductor portions 510, 520, 530, 540 and 550of the resonators 51 to 55 are located at the same position in themultilayer stack 20 in the first direction, i.e., the Z direction.

The conductor layer 311 forming the first input/output port 3 isconnected to the conductor layer 381 shown in FIG. 8 via the throughhole 31T1, the conductor layer 321 and the through holes 32T1, 33T1,34T1 and 35T1. The conductor layer 381 is opposed to a portion of theresonator conductor portion 510 (FIG. 9) near the first end 510 a withthe dielectric layer 38 interposed therebetween. The capacitor C1 shownin FIG. 2 is composed of the conductor layer 381 and the resonatorconductor portion 510, and also the dielectric layer 38 interposedtherebetween.

The conductor layer 312 forming the second input/output port 4 isconnected to the conductor layer 382 shown in FIG. 8 via the throughhole 31T2, the conductor layer 322 and the through holes 32T2, 33T2,34T2 and 35T2. The conductor layer 382 is opposed to a portion of theresonator conductor portion 550 (FIG. 9) near the first end 550 a withthe dielectric layer 38 interposed therebetween. The capacitor C2 shownin FIG. 2 is composed of the conductor layer 382 and the resonatorconductor portion 550, and also the dielectric layer 38 interposedtherebetween.

The conductor layer 383 shown in FIG. 8 is opposed to a portion of theresonator conductor portion 510 near the second end 510 b and to aportion of the resonator conductor portion 520 near the first end 520 a,with the dielectric layer 38 interposed between the conductor layer 383and each of the aforementioned respective portions of the resonatorconductor portions 510 and 520. The capacitor C12 shown in FIG. 2 iscomposed of the conductor layer 383, the resonator conductor portions510 and 520, and the dielectric layer 38 interposed between theconductor layer 383 and the resonator conductor portions 510 and 520.

The conductor layer 384 shown in FIG. 8 is opposed to a portion of theresonator conductor portion 520 near the second end 520 b and to aportion of the resonator conductor portion 530 near the first end 530 a,with the dielectric layer 38 interposed between the conductor layer 384and each of the aforementioned respective portions of the resonatorconductor portions 520 and 530. The capacitor C23 shown in FIG. 2 iscomposed of the conductor layer 384, the resonator conductor portions520 and 530, and the dielectric layer 38 interposed between theconductor layer 384 and the resonator conductor portions 520 and 530.

The conductor layer 385 shown in FIG. 8 is opposed to a portion of theresonator conductor portion 530 near the second end 530 b and to aportion of the resonator conductor portion 540 near the second end 540b, with the dielectric layer 38 interposed between the conductor layer385 and each of the aforementioned respective portions of the resonatorconductor portions 530 and 540. The capacitor C34 shown in FIG. 2 iscomposed of the conductor layer 385, the resonator conductor portions530 and 540, and the dielectric layer 38 interposed between theconductor layer 385 and the resonator conductor portions 530 and 540.

The conductor layer 386 shown in FIG. 8 is opposed to a portion of theresonator conductor portion 540 near the first end 540 a and to aportion of the resonator conductor portion 550 near the second end 550b, with the dielectric layer 38 interposed between the conductor layer386 and each of the aforementioned respective portions of the resonatorconductor portions 540 and 550. The capacitor C45 shown in FIG. 2 iscomposed of the conductor layer 386, the resonator conductor portions540 and 550, and the dielectric layer 38 interposed between theconductor layer 386 and the resonator conductor portions 540 and 550.

Each of the five through hole lines 7T of the first partition 7 isformed by connecting the through holes 7T1, 7T2, 7T3, 7T4, 7T5, 7T8, 7T9and 7T10 in series in the Z direction.

In the example shown in FIG. 3 to FIG. 11, part of the first partition 7extends to pass between the second portion 510B of the resonatorconductor portion 510 and the second portion 550B of the resonatorconductor portion 550, and is in contact with the first portion 61 andthe second portion 62.

Each of the five through hole lines 8T of the second partition 8 isformed by connecting the through holes 8T1, 8T2, 8T3, 8T4, 8T5, 8T8, 8T9and 8T10 in series in the Z direction.

Each of the plurality of through hole lines 63T of the connectingportion 63 is formed by connecting the through holes 63T1, 63T2, 63T3,63T4, 63T5, 63T8, 63T9 and 63T10 in series in the Z direction.

In the present embodiment, the resonators 51 and 55 which are notadjacent to each other in circuit configuration are magnetically coupledto each other, while the resonators 52 and 54 which are not adjacent toeach other in circuit configuration are capacitively coupled to eachother. The resonator 51 and the resonator 52 are adjacent to each otherin circuit configuration and are also capacitively coupled to eachother. The resonator 55 and the resonator 54 are adjacent to each otherin circuit configuration and are also capacitively coupled to eachother. The resonator conductor portions 510, 520, 540, and 550 of theresonators 51, 52, 54, and 55 having such relationships in circuitconfiguration have the following physical relationships with each other.

The resonator conductor portion 510 of the resonator 51 and theresonator conductor portion 550 of the resonator 55 are physicallyadjacent to each other without any resonator conductor portion ofanother resonator therebetween. In the present embodiment, inparticular, the second portion 510B of the resonator conductor portion510 and the second portion 550B of the resonator conductor portion 550,both of which extend in the Y direction, are physically adjacent to eachother in the X direction without any resonator conductor portion ofanother resonator therebetween. The magnetic coupling between theresonators 51 and 55 is thereby achieved.

The resonator conductor portion 520 of the resonator 52 and theresonator conductor portion 540 of the resonator 54 are physicallyadjacent to each other without any resonator conductor portion ofanother resonator therebetween. In the present embodiment, inparticular, the first end 520 a of the resonator conductor portion 520and the first end 540 a of the resonator conductor portion 540 are at asmall distance from each other and adjacent to each other, without anyresonator conductor portion of another resonator therebetween. Thecapacitive coupling between the resonators 52 and 54 is therebyachieved.

The resonator conductor portion 510 of the resonator 51 and theresonator conductor portion 520 of the resonator 52 are physicallyadjacent to each other without any resonator conductor portion ofanother resonator therebetween. The capacitive coupling between theresonators 51 and 52 is thereby achieved easily.

The resonator conductor portion 540 of the resonator 54 and theresonator conductor portion 550 of the resonator 55 are physicallyadjacent to each other without any resonator conductor portion ofanother resonator therebetween. The capacitive coupling between theresonators 54 and 55 is thereby achieved easily.

The function and effects of the band-pass filter 1 according to thepresent embodiment will now be described. For example, the band-passfilter 1 is designed and configured to have a passband in aquasi-millimeter wave band of 10 to 30 GHz or a millimeter wave band of30 to 300 GHz.

The band-pass filter 1 includes the resonators 51, 52, 53, 54 and 55which are provided between the first input/output port 3 and the secondinput/output port 4 and arranged in the listed order, from closest tofarthest from the first input/output port 3. The resonators 51 to 55 areconfigured so that electromagnetic coupling, more specifically,capacitive coupling, is established between every two of the resonatorsadjacent to each other in circuit configuration.

The band-pass filter 1 includes the shield 6. The shield 6 has thefunction of preventing electromagnetic radiation to the surroundings ofthe band-pass filter 1. In the present embodiment, the shield 6 and thedielectric inside the shield 6 constitute a structure similar to awaveguide, thereby generating one or more waveguide modes. The one ormore waveguide modes usually have resonance frequencies in a frequencyregion higher than the passband of the band-pass filter 1. If one of thewaveguide modes that is the lowest in resonance frequency, i.e., thelowest-order waveguide mode, has a resonance frequency relatively closeto the passband of the band-pass filter 1, there occurs the problem thatthe attenuation characteristic in the frequency region above thepassband deteriorates due to unwanted resonance at the resonancefrequency of the lowest-order waveguide mode.

The band-pass filter 1 according to the present embodiment prevents theoccurrence of the foregoing problem by the provision of the first andsecond partitions 7 and 8. This will be described in detail below.Assuming that there are no partitions 7 and 8, the resonance frequencyof the lowest-order waveguide mode depends on the shape of the spacedefined by the shield 6. Typically, the larger the space, the lower theresonance frequency of the lowest-order waveguide mode.

In the present embodiment, the first and second partitions 7 and 8divide the space defined by the shield 6 into a plurality of spaces.Specifically, in the present embodiment, the first partition 7 dividesthe space defined by the shield 6 into a space in which the resonatorconductor portion 510 is located and a space in which the resonatorconductor portion 550 is located.

In the present embodiment, the resonance frequency of the lowest-orderwaveguide mode depends on the shape of each of the plurality of spacesdivided by the first and second partitions 7 and 8. Each of theseplurality of spaces is smaller than the space defined by the shield 6 inthe absence of the partitions 7 and 8. The present invention thus makesthe resonance frequency of the lowest-order waveguide mode higher thanin the case where there are no partitions 7 and 8. Consequently, theband-pass filter 1 according to the present embodiment prevents theattenuation characteristic in the frequency region above the passbandfrom being degraded by the lowest-order waveguide mode.

In the present embodiment, the first stage resonator 51 and the fifthstage resonator 55, which are not adjacent to each other in circuitconfiguration, are magnetically coupled to each other. This enablescreation of an attenuation pole in at least one of two frequency regionsin a frequency response of insertion loss. One of the two frequencyregions is a first passband-vicinity region, which is a frequency regionclose to the passband and lower than the passband, and the other is asecond passband-vicinity region, which is a frequency region close tothe passband and higher than the passband. Note that the passband is,for example, a frequency band between two frequencies at which theinsertion loss becomes higher by 3 dB than its minimum value.

In the present embodiment, specifically, the magnetic coupling betweenthe first stage resonator 51 and the fifth stage resonator 55 creates anattenuation pole in the first passband-vicinity region.

In the present embodiment, the second stage resonator 52 and the fourthstage resonator 54, which are not adjacent to each other in circuitconfiguration, are capacitively coupled to each other. This enablescreation of an attenuation pole in the second passband-vicinity region.

By virtue of these features, the present embodiment provides theband-pass filter 1 which includes the five resonators 51 and 55 and theshield 6 and has favorable characteristics. In the present embodiment,the favorable characteristics of the band-pass filter 1 specificallyrefer to steep changes in the insertion loss in both of the first andsecond passband-vicinity regions, and prevention of deterioration in theattenuation characteristic associated with the lowest-order waveguidemode.

In the present embodiment, at least part of the first partition 7extends to pass between the resonator conductor portion 510 and theresonator conductor portion 550. The resonator conductor portion 510 andthe resonator conductor portion 550 respectively constitute theresonator 51 and the resonator 55, which are magnetically coupled toeach other although not adjacent to each other in circuit configuration.The magnetic coupling between the resonators 51 and 55 can be weakerthan the electromagnetic coupling between any two resonators that areadjacent to each other in circuit configuration. According to thepresent embodiment, it is thus possible to establish magnetic couplingbetween the resonators 51 and 55 while disposing the first partition 7such that at least part thereof passes between the resonator conductorportion 510 and the resonator conductor portion 550. The presentembodiment thus achieves both of prevention of deterioration in theattenuation characteristic associated with the lowest-order waveguidemode by the provision of the first partition 7 and the creation of anattenuation pole by establishing magnetic coupling between theresonators 51 and 55. This results in the favorable characteristics ofthe band-pass filter 1.

Each of the five resonators 51 to 55 in the present embodiment is ahalf-wave resonator. In this case, each of the resonator conductorportions 510, 520, 530, 540 and 550 may have a harmonic resonance modein addition to a basic resonance mode, the basic resonance mode having abasic resonance frequency which determines the passband, the harmonicresonance mode having a resonance frequency twice as high as the basicresonance frequency. The harmonic resonance mode may degrade theattenuation characteristic in a frequency region above the passband.

To address this problem, the band-pass filter 1 according to the presentembodiment has the notch filter section capable of attenuating signalshaving a resonance frequency twice as high as the basic resonancefrequency. The present embodiment thereby prevents the attenuationcharacteristic from being degraded by the harmonic resonance mode.

In the present embodiment, the resonator conductor portions 510, 520,540 and 550 of the resonators 51, 52, 54 and 55 having theabove-described relationship in circuit configuration are configured tohave the above-described physical relationship. The present embodimentthus realizes the band-pass filter 1 which has two cross couplings andis simple in structure.

Now, an example of characteristics of the band-pass filter 1 accordingto the present embodiment and an example of characteristics of aband-pass filter of a first comparative example will be discussed. Theband-pass filter of the first comparative example has the sameconfiguration as that of the band-pass filter 1 except that the firstpartition 7 is omitted.

FIG. 12 illustrates an example frequency response of the insertion lossof the band-pass filter 1 according to the present embodiment. FIG. 13illustrates an example frequency response of the insertion loss of theband-pass filter of the first comparative example. The frequencyresponses shown in FIGS. 12 and 13 were obtained by simulation. In FIGS.12 and 13, the horizontal axis represents frequency, and the verticalaxis represents insertion loss. In the examples shown in FIGS. 12 and13, the band-pass filter 1 and the band-pass filter of the firstcomparative example have a passband of approximately 26 to 30 GHz, andthe center frequency of the passband is approximately 28 GHz.

For the band-pass filter 1 used in the simulation, the magnitudes of thetwo cross couplings were adjusted, based on the presence of the firstpartition 7, so as to create attenuation poles in both of the firstpassband-vicinity region and the second passband-vicinity region, asshown in FIG. 12. The first passband-vicinity region is a frequencyregion of approximately 24 to 26 GHz. The second passband-vicinityregion is a frequency region of approximately 30 to 32 GHz. Asillustrated in FIG. 13, the characteristic of the band-pass filter ofthe first comparative example shows no attenuation pole in the firstpassband-vicinity region, and shows a lower insertion loss than that ofthe band-pass filter 1 at an attenuation pole in the secondpassband-vicinity region. This is because, for the band-pass filter ofthe first comparative example, the omission of the first partition 7resulted in a deviation of the magnitude of the magnetic couplingbetween the resonators 51 and 55 from the adjusted magnitude in theband-pass filter 1.

Further, the characteristic of the band-pass filter of the firstcomparative example shown in FIG. 13 exhibits a peak of an extremereduction in the insertion loss at approximately 40 GHz. This isconsidered to be due to unwanted resonance caused by the lowest-orderwaveguide mode at approximately 40 GHz. In contrast, the characteristicof the band-pass filter 1 shown in FIG. 12 exhibits no such peak as thatoccurring in the characteristic shown in FIG. 13, and thus exhibits abetter attenuation characteristic in a frequency region above thepassband, when compared with the characteristic shown in FIG. 13.

Further, the characteristic of the band-pass filter 1 shown in FIG. 12exhibits an increase in the insertion loss at approximately 55 GHz. Thisis due to the effect of the notch filter section.

It is apparent from FIG. 12 that the band-pass filter 1 according to thepresent embodiment provides the favorable characteristics achievingsteep changes in the insertion loss in both of the first and secondpassband-vicinity regions and prevention of deterioration in theattenuation characteristic associated with the lowest-order waveguidemode.

Second Embodiment

A second embodiment of the present invention will now be described.First, the configuration of a band-pass filter according to the presentembodiment will be described with reference to FIG. 14 and FIG. 15. FIG.14 is a perspective view illustrating the structure of the band-passfilter according to the second embodiment. FIG. 15 is a circuit diagramillustrating the circuit configuration of the band-pass filter accordingto the second embodiment.

The band-pass filter 100 according to the present embodiment includesthe main body 2, the first input/output port 3, the second input/outputport 4, five or more resonators, the shield 6, a partition 107, and acoupling adjustment section 108. The main body 2 includes the multilayerstack 20.

The five or more resonators are located between the first input/outputport 3 and the second input/output port 4 in circuit configuration. Inthe present embodiment, the five or more resonators are six resonators151, 152, 153, 154, 155 and 156. The six resonators 151, 152, 153, 154,155 and 156 are arranged in this order, from closest to farthest, fromthe first input/output port 3 in circuit configuration. The sixresonators 151 to 156 are configured so that electromagnetic coupling isestablished between every two of the resonators adjacent to each otherin circuit configuration. Specifically, the resonators 151 to 156 areconfigured so that the resonators 151 and 152 are adjacent to each otherin circuit configuration and are electromagnetically coupled to eachother, the resonators 152 and 153 are adjacent to each other in circuitconfiguration and are electromagnetically coupled to each other, theresonators 153 and 154 are adjacent to each other in circuitconfiguration and are electromagnetically coupled to each other, theresonators 154 and 155 are adjacent to each other in circuitconfiguration and are electromagnetically coupled to each other, and theresonators 155 and 156 are adjacent to each other in circuitconfiguration and are electromagnetically coupled to each other. In thepresent embodiment, the electromagnetic coupling between every two ofthe resonators adjacent to each other in circuit configuration isspecifically capacitive coupling. In the present embodiment, each of theresonators 151 to 156 is a resonator with open ends, and also ahalf-wave resonator.

The first portion 61, the second portion 62 and the connecting portion63 of the shield 6 are arranged to surround the six resonators 151 to156. The first portion 61 is formed of a first conductor layer 1313disposed on the first end face 21 a of the main portion 21 of themultilayer stack 20. The second portion 62 is formed of a secondconductor layer 1521 disposed on the second end face 21 b of the mainportion 21 of the multilayer stack 20.

The band-pass filter 100 includes a capacitor C112 for establishingcapacitive coupling between the resonators 151 and 152, a capacitor C123for establishing capacitive coupling between the resonators 152 and 153,a capacitor C134 for establishing capacitive coupling between theresonators 153 and 154, a capacitor C145 for establishing capacitivecoupling between the resonators 154 and 155, and a capacitor C156 forestablishing capacitive coupling between the resonators 155 and 156.

In the present embodiment, among the six resonators 151 to 156, theresonator 152, which is the second closest to the first input/outputport 3 in circuit configuration, and the resonator 155, which is thesecond closest to the second input/output port 4 in circuitconfiguration, are magnetically coupled to each other although they arenot adjacent to each other in circuit configuration. The resonator 152corresponds to the first resonator in the present invention. Theresonator 155 corresponds to the second resonator in the presentinvention.

Further, in the present embodiment, among the six resonators 151 to 156,the resonator 151, which is the closest to the first input/output port 3in circuit configuration, and the resonator 156, which is the closest tothe second input/output port 4 in circuit configuration, arecapacitively coupled to each other although they are not adjacent toeach other in circuit configuration. The resonator 151 corresponds tothe third resonator in the present invention. The resonator 156corresponds to the fourth resonator in the present invention. In FIG.15, the capacitor symbol C116 represents the capacitive coupling betweenthe resonators 151 and 156.

The band-pass filter 100 further includes a capacitor C101 providedbetween the first input/output port 3 and the resonator 151, and acapacitor C102 provided between the second input/output port 4 and theresonator 156.

The band-pass filter 100 further includes the two lines 91 and 92 as inthe first embodiment.

The resonator 151 includes a resonator conductor portion 1510 formed ofa conductor. The resonator 152 includes a resonator conductor portion1520 formed of a conductor. The resonator 153 includes a resonatorconductor portion 1530 formed of a conductor. The resonator 154 includesa resonator conductor portion 1540 formed of a conductor. The resonator155 includes a resonator conductor portion 1550 formed of a conductor.The resonator 156 includes a resonator conductor portion 1560 formed ofa conductor.

Each of the resonator conductor portions 1510, 1520, 1530, 1540, 1550and 1560 extends in a direction intersecting the first direction or theZ direction. In the present embodiment, specifically, each of theresonator conductor portions 1510, 1520, 1530, 1540, 1550 and 1560extends in a direction orthogonal to the first direction or the Zdirection.

Each of the resonator conductor portions 1510, 1520, 1530, 1540, 1550and 1560 has a first end and a second end opposite to each other. Asmentioned above, each of the resonators 151 to 156 is a resonator withopen ends. Thus, both of the first and second ends of each of theresonator conductor portions 1510, 1520, 1530, 1540, 1550 and 1560 areopen. Each of the resonator conductor portions 1510, 1520, 1530, 1540,1550 and 1560 has a length of one half or nearly one half the wavelengthcorresponding to the center frequency of the passband of the band-passfilter 100.

The partition 107 is in contact with the first portion 61 and the secondportion 62. At least part of the partition 107 extends to pass betweenthe resonator conductor portion 1520 and the resonator conductor portion1550. In the present embodiment, specifically, the partition 107 extendsin the first direction, i.e., the Z direction. The partition 107connects the first portion 61 and the second portion 62 via the shortestpath. To be more specific, the length of the partition 107 in the Zdirection is equal to the distance between the first portion 61 and thesecond portion 62.

The partition 107 runs through the two or more dielectric layersconstituting the main portion 21. In the present embodiment, thepartition 107 includes a plurality of through hole lines 107T eachrunning through the two or more dielectric layers constituting the mainportion 21, and includes a conductor layer 107C. The plurality ofthrough hole lines 107T correspond to the plurality of first throughhole lines in the present invention. In FIG. 14, each through hole line107T is represented by a circular column. Each of the through hole lines107T includes two or more through holes connected in series. Each of thethrough hole lines 107T extends in the Z direction. The through holelines 107T are arranged to be adjacent to each other in the Y direction.In the present embodiment, the number of the through hole lines 107T isseven.

The coupling adjustment section 108 is intended to adjust the magnitudeof the capacitive coupling between the resonators 151 and 156. Thecoupling adjustment section 108 includes a plurality of through holelines 108T each running through the two or more dielectric layersconstituting the main portion 21. In FIG. 14, each through hole line108T is represented by a circular column. Each of the through hole lines108T includes two or more through holes connected in series. Each of thethrough hole lines 108T extends in the Z direction, and is in contactwith the first portion 61 and the second portion 62. The through holelines 108T are arranged to be adjacent to each other in the Y directionin the vicinity of the second end of the resonator conductor portion1510 and the second end of the resonator conductor portion 1560. In thepresent embodiment, the number of the through hole lines 108T is two.

The connecting portion 63 of the shield 6 includes a plurality ofthrough hole lines 163T each running through the two or more dielectriclayers constituting the main portion 21. The plurality of through holelines 163T correspond to the second through hole lines in the presentinvention. In FIG. 14, each through hole line 163T is represented by acircular column. All the through hole lines represented by circularcolumns in FIG. 14, except the seven through hole lines 107T and the twothrough hole lines 108T, are the through hole lines 163T. Each of thethrough hole lines 163T includes two or more through holes connected inseries. Each of the through hole lines 163T extends in the Z direction.

Reference is now made to FIG. 16 to FIG. 24 to describe an example of aplurality of dielectric layers constituting the multilayer stack 20 andthe configuration of a plurality of conductor layers formed on thedielectric layers and a plurality of through holes formed in thedielectric layers. In this example, the multilayer stack 20 includestwenty-two dielectric layers stacked together. The twenty-two dielectriclayers will be referred to as the first to twenty-second dielectriclayers in the order from bottom to top. The first to twenty-seconddielectric layers are denoted by reference numerals 131 to 152,respectively. The main portion 21 is composed of the first totwenty-first dielectric layers 131 to 151. The coating portion 22 iscomposed of the twenty-second dielectric layer 152. In FIG. 16 to FIG.23, each circle represents a through hole.

FIG. 16 illustrates a patterned surface of the first dielectric layer131. On the patterned surface of the first dielectric layer 131, thereare formed a conductor layer 1311 forming the first input/output port 3,a conductor layer 1312 forming the second input/output port 4, and thefirst conductor layer 1313 forming the first portion 61 of the shield 6.

Further, a through hole 131T1 connected to the conductor layer 1311, anda through hole 131T2 connected to the conductor layer 1312 are formed inthe dielectric layer 131. Further formed in the dielectric layer 131 areseven through holes 107T1 constituting respective portions of the seventhrough hole lines 107T, two through holes 108T1 constituting respectiveportions of the two through hole lines 108T, and a plurality of throughholes 163T1 constituting respective portions of the plurality of throughhole lines 163T. All the through holes represented by circles in FIG.16, except the through holes 131T1, 131T2, 107T1 and 108T1, are thethrough holes 163T1. The through holes 107T1, 108T1 and 163T1 areconnected to the first conductor layer 1313. FIG. 17 illustrates apatterned surface of each of the second and third dielectric layers 132and 133. Through holes 132T1 and 132T2 are formed in each of thedielectric layers 132 and 133. The through holes 131T1 and 131T2 shownin FIG. 16 are connected to the through holes 132T1 and 132T2,respectively.

In each of the dielectric layers 132 and 133, there are further formedseven through holes 107T2 constituting respective portions of the seventhrough hole lines 107T. The seven through holes 107T1 shown in FIG. 16are respectively connected to the seven through holes 107T2 formed inthe second dielectric layer 132.

In each of the dielectric layers 132 and 133, there are further formedtwo through holes 108T2 constituting respective portions of the twothrough hole lines 108T. The two through holes 108T1 shown in FIG. 16are respectively connected to the two through holes 108T2 formed in thesecond dielectric layer 132.

Further, a plurality of through holes 163T2 constituting respectiveportions of the plurality of through hole lines 163T are formed in eachof the dielectric layers 132 and 133. All the through holes representedby circles in FIG. 17, except the through holes 132T1, 132T2, 107T2 and108T2, are the through holes 163T2. The plurality of through holes 163T1shown in FIG. 16 are respectively connected to the plurality of throughholes 163T2 formed in the second dielectric layer 132.

In the dielectric layers 132 and 133, every vertically adjacent throughholes denoted by the same reference signs are connected to each other.

FIG. 18 illustrates a patterned surface of the fourth dielectric layer134. On the patterned surface of the dielectric layer 134, there areformed a conductor layer 1341 forming the line 91 and a conductor layer1342 forming the line 92. Each of the conductor layers 1341 and 1342 hasa first end and a second end opposite to each other. The through hole132T1 formed in the third dielectric layer 133 is connected to a portionof the conductor layer 1341 near the first end thereof. The through hole132T2 formed in the third dielectric layer 133 is connected to a portionof the conductor layer 1342 near the first end thereof. A portion of theconductor layer 1341 near the second end thereof and a portion of theconductor layer 1342 near the second end thereof are opposed to theconductor layer 1313 shown in FIG. 16 with the dielectric layers 131,132 and 133 interposed between the conductor layer 1313 and each of theaforementioned portions of the conductor layers 1341 and 1342.

Further formed in the dielectric layer 134 are a through hole 134T1connected to the portion of the conductor layer 1341 near the first endthereof, and a through hole 134T2 connected to the portion of theconductor layer 1342 near the first end thereof.

Further, seven through holes 107T4 constituting respective portions ofthe seven through hole lines 107T are formed in the dielectric layer134. The seven through holes 107T2 formed in the third dielectric layer133 are connected to the seven through holes 107T4, respectively.

Further formed in the dielectric layer 134 are two through holes 108T4constituting respective portions of the two through hole lines 108T. Thetwo through holes 108T2 formed in the third dielectric layer 133 areconnected to the two through holes 108T4, respectively.

Further formed in the dielectric layer 134 are a plurality of throughholes 163T4 constituting respective portions of the plurality of throughhole lines 163T. All the through holes represented by circles in FIG.18, except the through holes 134T1, 134T2, 107T4 and 108T4, are thethrough holes 163T4. The plurality of through holes 163T2 formed in thethird dielectric layer 133 are connected to the plurality of throughholes 163T4, respectively.

FIG. 19 illustrates a patterned surface of each of the fifth to ninthdielectric layers 135 to 139. Through holes 135T1 and 135T2 are formedin each of the dielectric layers 135 to 139. The through holes 134T1 and134T2 shown in FIG. 18 are respectively connected to the through holes135T1 and 135T2 formed in the fifth dielectric layer 135.

In each of the dielectric layers 135 to 139, there are further formedseven through holes 107T5 constituting respective portions of the seventhrough hole lines 107T. The seven through holes 107T4 shown in FIG. 18are respectively connected to the seven through holes 107T5 formed inthe fifth dielectric layer 135.

In each of the dielectric layers 135 to 139, there are further formedtwo through holes 108T5 constituting respective portions of the twothrough hole lines 108T. The two through holes 108T4 shown in FIG. 18are respectively connected to the two through holes 108T5 formed in thefifth dielectric layer 135.

Further, a plurality of through holes 163T5 constituting respectiveportions of the plurality of through hole lines 163T are formed in eachof the dielectric layers 135 to 139. All the through holes representedby circles in FIG. 19, except the through holes 135T1, 135T2, 107T5 and108T5, are the through holes 163T5. The plurality of through holes 163T4shown in FIG. 18 are respectively connected to the plurality of throughholes 163T5 formed in the fifth dielectric layer 135.

In the dielectric layers 135 to 139, every vertically adjacent throughholes denoted by the same reference signs are connected to each other.

FIG. 20 illustrates a patterned surface of the tenth dielectric layer140. On the patterned surface of the dielectric layer 140, there areformed a conductor layer 1401 for forming the capacitor C101 shown inFIG. 15 and a conductor layer 1402 for forming the capacitor C102 shownin FIG. 15. The through hole 135T1 formed in the ninth dielectric layer139 is connected to the conductor layer 1401. The through hole 135T2formed in the ninth dielectric layer 139 is connected to the conductorlayer 1402.

On the patterned surface of the dielectric layer 140, there are furtherformed conductor layers 1403, 1404, 1405, 1406 and 1407 for forming thecapacitors C112, C123, C134, C145 and C156 shown in FIG. 15,respectively.

Further, seven through holes 107T10 constituting respective portions ofthe seven through hole lines 107T are formed in the dielectric layer140. The seven through holes 107T5 formed in the ninth dielectric layer139 are connected to the seven through holes 107T10, respectively.

Further formed in the dielectric layer 140 are two through holes 108T10constituting respective portions of the two through hole lines 108T. Thetwo through holes 108T5 formed in the ninth dielectric layer 139 areconnected to the two through holes 108T10, respectively.

Further formed in the dielectric layer 140 are a plurality of throughholes 163T10 constituting respective portions of the plurality ofthrough hole lines 163T. All the through holes represented by circles inFIG. 20, except the through holes 107T10 and 108T10, are the throughholes 163T10. The plurality of through holes 163T5 formed in the ninthdielectric layer 139 are connected to the plurality of through holes163T10, respectively.

FIG. 21 illustrates a patterned surface of the eleventh dielectric layer141. In the dielectric layer 141, there are formed seven through holes107T11 constituting respective portions of the seven through hole lines107T. The seven through holes 107T10 shown in FIG. 20 are connected tothe seven through holes 107T11, respectively.

Further formed in the dielectric layer 141 are two through holes 108T11constituting respective portions of the two through hole lines 108T. Thetwo through holes 108T10 shown in FIG. 20 are connected to the twothrough holes 108T11, respectively.

Further formed in the dielectric layer 141 are a plurality of throughholes 163T11 constituting respective portions of the plurality ofthrough hole lines 163T. All the through holes represented by circles inFIG. 21, except the through holes 107T11 and 108T11, are the throughholes 163T11. The plurality of through holes 163T10 shown in FIG. 20 areconnected to the plurality of through holes 163T11, respectively.

FIG. 22 illustrates a patterned surface of the twelfth dielectric layer142. The resonator conductor portions 1510, 1520, 1530, 1540, 1550 and1560 are formed on the patterned surface of the dielectric layer 142.

The resonator conductor portion 1510 has a first end 1510 a and a secondend 1510 b opposite to each other. The resonator conductor portion 1520has a first end 1520 a and a second end 1520 b opposite to each other.The resonator conductor portion 1530 has a first end 1530 a and a secondend 1530 b opposite to each other. The resonator conductor portion 1540has a first end 1540 a and a second end 1540 b opposite to each other.The resonator conductor portion 1550 has a first end 1550 a and a secondend 1550 b opposite to each other. The resonator conductor portion 1560has a first end 1560 a and a second end 1560 b opposite to each other.

Each of the resonator conductor portions 1510 and 1560 extends in the Xdirection. The resonator conductor portions 1510 and 1560 are arrangedin such a positional relationship that one straight line extends acrossthe resonator conductor portions 1510 and 1560 in the X direction. Thesecond end 1510 b of the resonator conductor portion 1510 and the secondend 1560 b of the resonator conductor portion 1560 are at apredetermined distance from each other and adjacent to each other. Thedistance between the second end 1510 b and the second end 1560 b issufficiently smaller than the length of each of the resonator conductorportions 1510 and 1560.

Each of the resonator conductor portions 1520 and 1550 extends in the Ydirection. The resonator conductor portions 1520 and 1550 are at apredetermined distance from each other and adjacent to each other in theX direction. The distance between the resonator conductor portions 1520and 1550 is smaller than the length of each of the resonator conductorportions 1520 and 1550.

The first end 1520 a of the resonator conductor portion 1520 is locatednear the second end 1510 b of the resonator conductor portion 1510. Thefirst end 1550 a of the resonator conductor portion 1550 is located nearthe second end 1560 b of the resonator conductor portion 1560.

The resonator conductor portion 1530 includes a first portion 1530A, asecond portion 1530B and a third portion 1530C. The first portion 1530Aincludes the first end 1530 a, and the second portion 1530B includes thesecond end 1530 b. The first portion 1530A extends in the X direction,and the second portion 1530B extends in the Y direction. The thirdportion 1530C connects an end of the first portion 1530A opposite fromthe first end 1530 a and an end of the second portion 1530B oppositefrom the second end 1530 b. In FIG. 22, the boundary between the firstportion 1530A and the third portion 1530C and the boundary between thesecond portion 1530B and the third portion 1530C are shown by brokenlines. The first end 1530 a is located near the second end 1520 b of theresonator conductor portion 1520.

The resonator conductor portion 1540 includes a first portion 1540A, asecond portion 1540B and a third portion 1540C. The first portion 1540Aincludes the first end 1540 a, and the second portion 1540B includes thesecond end 1540 b. The first portion 1540A extends in the X direction,and the second portion 1540B extends in the Y direction. The thirdportion 1540C connects an end of the first portion 1540A opposite fromthe first end 1540 a and an end of the second portion 1540B oppositefrom the second end 1540 b. In FIG. 22, the boundary between the firstportion 1540A and the third portion 1540C and the boundary between thesecond portion 1540B and the third portion 1540C are shown by brokenlines. The first end 1540 a is located near the second end 1550 b of theresonator conductor portion 1550.

The first end 1530 a of the resonator conductor portion 1530 and thefirst end 1540 a of the resonator conductor portion 1540 are at apredetermined distance from each other and adjacent to each other.

The conductor layer 107C constituting part of the partition 107 isfurther formed on the patterned surface of the dielectric layer 142. Theconductor layer 107C is situated between the resonator conductor portion1520 and the resonator conductor portion 1550, and extends in the Ydirection.

Further, seven through holes 107T12 constituting respective portions ofthe seven through hole lines 107T are formed in the dielectric layer142. The seven through holes 107T12 are connected to the conductor layer107C. The seven through holes 107T11 shown in FIG. 21 are connected tothe seven through holes 107T12, respectively.

Further formed in the dielectric layer 142 are two through holes 108T12constituting respective portions of the two through hole lines 108T. Thetwo through holes 108T11 shown in FIG. 21 are connected to the twothrough holes 108T12, respectively.

Further formed in the dielectric layer 142 are a plurality of throughholes 163T12 constituting respective portions of the plurality ofthrough hole lines 163T. All the through holes represented by circles inFIG. 22, except the through holes 107T12 and 108T12, are the throughholes 163T12. The plurality of through holes 163T11 shown in FIG. 21 areconnected to the plurality of through holes 163T12, respectively.

FIG. 23 illustrates a patterned surface of each of the thirteenth totwenty-first dielectric layers 143 to 151. Seven through holes 107T13constituting respective portions of the seven through hole lines 107Tare formed in each of the dielectric layers 143 to 151. The seventhrough holes 107T12 shown in FIG. 22 are respectively connected to theseven through holes 107T13 formed in the thirteenth dielectric layer143.

In each of the dielectric layers 143 to 151, there are further formedtwo through holes 108T13 constituting respective portions of the twothrough hole lines 108T. The two through holes 108T12 shown in FIG. 22are respectively connected to the two through holes 108T13 formed in thethirteenth dielectric layer 143.

Further, a plurality of through holes 163T13 constituting respectiveportions of the plurality of through hole lines 163T are formed in eachof the dielectric layers 143 to 151. All the through holes representedby circles in FIG. 23, except the through holes 107T13 and 108T13, arethe through holes 163T13. The plurality of through holes 163T12 shown inFIG. 22 are respectively connected to the plurality of through holes163T13 formed in the thirteenth dielectric layer 143.

In the dielectric layers 143 to 151, every vertically adjacent throughholes denoted by the same reference signs are connected to each other.

FIG. 24 illustrates a patterned surface of the twenty-second dielectriclayer 152. The second conductor layer 1521 forming the second portion 62of the shield 6 is formed on the patterned surface of the dielectriclayer 152. The through holes 107T13, 108T13 and 163T13 formed in thetwenty-first dielectric layer 151 are connected to the second conductorlayer 1521.

The band-pass filter 100 according to the present embodiment is formedby stacking the first to twenty-second dielectric layers 131 to 152 suchthat the patterned surface of the first dielectric layer 131 also servesas the first end face 2A of the main body 2. A surface of thetwenty-second dielectric layer 152 opposite to the patterned surfaceserves as the second end face 2B of the main body 2. The first totwenty-second dielectric layers 131 to 152 constitute the multilayerstack 20.

The respective resonator conductor portions 1510, 1520, 1530, 1540, 1550and 1560 of the resonators 151 to 156 are located at the same positionin the multilayer stack 20 in the first direction, i.e., the Zdirection.

The conductor layer 1311 forming the first input/output port 3 isconnected to the conductor layer 1401 shown in FIG. 20 via the throughholes 131T1, 132T1, 134T1 and 135T1. The conductor layer 1401 is opposedto a portion of the resonator conductor portion 1510 (FIG. 22) near thefirst end 1510 a with the dielectric layers 140 and 141 interposedtherebetween. The capacitor C101 shown in FIG. 15 is composed of theconductor layer 1401 and the resonator conductor portion 1510, and alsothe dielectric layers 140 and 141 interposed therebetween.

The conductor layer 1312 forming the second input/output port 4 isconnected to the conductor layer 1402 shown in FIG. 20 via the throughholes 131T2, 132T2, 134T2 and 135T2. The conductor layer 1402 is opposedto a portion of the resonator conductor portion 1560 (FIG. 22) near thefirst end 1560 a with the dielectric layers 140 and 141 interposedtherebetween. The capacitor C102 shown in FIG. 15 is composed of theconductor layer 1402 and the resonator conductor portion 1560, and alsothe dielectric layers 140 and 141 interposed therebetween.

The conductor layer 1403 shown in FIG. 20 is opposed to a portion of theresonator conductor portion 1510 near the second end 1510 b and to aportion of the resonator conductor portion 1520 near the first end 1520a, with the dielectric layers 140 and 141 interposed between theconductor layer 1403 and each of the aforementioned respective portionsof the resonator conductor portions 1510 and 1520. The capacitor C112shown in FIG. 15 is composed of the conductor layer 1403, the resonatorconductor portions 1510 and 1520, and the dielectric layers 140 and 141interposed between the conductor layer 1403 and the resonator conductorportions 1510 and 1520.

The conductor layer 1404 shown in FIG. 20 is opposed to a portion of theresonator conductor portion 1520 near the second end 1520 b and to aportion of the resonator conductor portion 1530 near the first end 1530a, with the dielectric layers 140 and 141 interposed between theconductor layer 1404 and each of the aforementioned respective portionsof the resonator conductor portions 1520 and 1530. The capacitor C123shown in FIG. 15 is composed of the conductor layer 1404, the resonatorconductor portions 1520 and 1530, and the dielectric layers 140 and 141interposed between the conductor layer 1404 and the resonator conductorportions 1520 and 1530.

The conductor layer 1405 shown in FIG. 20 is opposed to a portion of theresonator conductor portion 1530 near the first end 1530 a and to aportion of the resonator conductor portion 1540 near the first end 1540a, with the dielectric layers 140 and 141 interposed between theconductor layer 1405 and each of the aforementioned respective portionsof the resonator conductor portions 1530 and 1540. The capacitor C134shown in FIG. 15 is composed of the conductor layer 1405, the resonatorconductor portions 1530 and 1540, and the dielectric layers 140 and 141interposed between the conductor layer 1405 and the resonator conductorportions 1530 and 1540.

The conductor layer 1406 shown in FIG. 20 is opposed to a portion of theresonator conductor portion 1540 near the first end 1540 a and to aportion of the resonator conductor portion 1550 near the second end 1550b, with the dielectric layers 140 and 141 interposed between theconductor layer 1406 and each of the aforementioned respective portionsof the resonator conductor portions 1540 and 1550. The capacitor C145shown in FIG. 15 is composed of the conductor layer 1406, the resonatorconductor portions 1540 and 1550, and the dielectric layers 140 and 141interposed between the conductor layer 1406 and the resonator conductorportions 1540 and 1550.

The conductor layer 1407 shown in FIG. 20 is opposed to a portion of theresonator conductor portion 1550 near the first end 1550 a and to aportion of the resonator conductor portion 1560 near the second end 1560b, with the dielectric layers 140 and 141 interposed between theconductor layer 1407 and each of the aforementioned respective portionsof the resonator conductor portions 1550 and 1560. The capacitor C156shown in FIG. 15 is composed of the conductor layer 1407, the resonatorconductor portions 1550 and 1560, and the dielectric layers 140 and 141interposed between the conductor layer 1407 and the resonator conductorportions 1550 and 1560.

Each of the seven through hole lines 107T of the partition 107 is formedby connecting the through holes 107T1, 107T2, 107T4, 107T5, 107T10,107T11, 107T12 and 107T13 in series in the Z direction.

In the example shown in FIG. 16 to FIG. 24, the partition 107 extends topass between the resonator conductor portion 1520 and the resonatorconductor portion 1550, and is in contact with the first portion 61 andthe second portion 62.

Each of the two through hole lines 108T of the coupling adjustmentsection 108 is formed by connecting the through holes 108T1, 108T2,108T4, 108T5, 108T10, 108T11, 108T12 and 108T13 in series in the Zdirection.

Each of the plurality of through hole lines 163T of the connectingportion 163 is formed by connecting the through holes 163T1, 163T2,163T4, 163T5, 163T10, 163T11, 163T12 and 163T13 in series in the Zdirection.

In the present embodiment, the resonators 152 and 155 which are notadjacent to each other in circuit configuration are magnetically coupledto each other, while the resonators 151 and 156 which are not adjacentto each other in circuit configuration are capacitively coupled to eachother. The resonator 152 and the resonator 151 are adjacent to eachother in circuit configuration and are also capacitively coupled to eachother. The resonator 155 and the resonator 156 are adjacent to eachother in circuit configuration and are also capacitively coupled to eachother. The resonator conductor portions 1510, 1520, 1550 and 1560 of theresonators 151, 152, 155 and 156 having such relationships in circuitconfiguration have the following physical relationships with each other.

The resonator conductor portion 1520 of the resonator 152 and theresonator conductor portion 1550 of the resonator 155 are physicallyadjacent to each other without any resonator conductor portion ofanother resonator therebetween. In the present embodiment, inparticular, the resonator conductor portion 1520 and the resonatorconductor portion 1550, both of which extend in the Y direction, arephysically adjacent to each other in the X direction without anyresonator conductor portion of another resonator therebetween. Themagnetic coupling between the resonators 152 and 155 is therebyachieved.

The resonator conductor portion 1510 of the resonator 151 and theresonator conductor portion 1560 of the resonator 156 are physicallyadjacent to each other without any resonator conductor portion ofanother resonator therebetween. In the present embodiment, inparticular, the second end 1510 b of the resonator conductor portion1510 and the second end 1560 b of the resonator conductor portion 1560are at a small distance from each other and adjacent to each other,without any resonator conductor portion of another resonatortherebetween. The capacitive coupling between the resonators 151 and 156is thereby achieved.

The resonator conductor portion 1520 of the resonator 152 and theresonator conductor portion 1510 of the resonator 151 are physicallyadjacent to each other without any resonator conductor portion ofanother resonator therebetween. The capacitive coupling between theresonators 152 and 151 is thereby achieved easily.

The resonator conductor portion 1550 of the resonator 155 and theresonator conductor portion 1560 of the resonator 156 are physicallyadjacent to each other without any resonator conductor portion ofanother resonator therebetween. The capacitive coupling between theresonators 155 and 156 is thereby achieved easily.

The function and effects of the band-pass filter 100 according to thepresent embodiment will now be described. For example, the band-passfilter 100 is designed and configured to have a passband in aquasi-millimeter wave band of 10 to 30 GHz or a millimeter wave band of30 to 300 GHz.

In the present embodiment, the partition 107 divides the space definedby the shield 6 into a space in which the resonator conductor portion1520 is located and a space in which the resonator conductor portion1550 is located. The present embodiment thus prevents the attenuationcharacteristic in the frequency region above the passband from beingdegraded by the lowest-order waveguide mode, like the first embodiment.

Further, in the present embodiment, the second stage resonator 152 andthe fifth stage resonator 155, which are not adjacent to each other incircuit configuration, are magnetically coupled to each other. Themagnetic coupling between the resonators 152 and 155 enables creation ofattenuation poles in both of the first and second passband-vicinityregions in the frequency response of the insertion loss, the firstpassband-vicinity region being close to the passband and lower than thepassband, the second passband-vicinity region being close to thepassband and higher than the passband.

In the present embodiment, the first stage resonator 151 and the sixthstage resonator 156, which are not adjacent to each other in circuitconfiguration, are capacitively coupled to each other. The capacitivecoupling between the resonators 151 and 156 has the effect of increasingthe insertion loss at the attenuation pole occurring in the firstpassband-vicinity region. The magnitude of the insertion loss at theattenuation pole occurring in the first passband-vicinity region isadjustable by adjusting the magnitude of the capacitive coupling betweenthe resonators 151 and 156. The coupling adjustment section 108 isprovided to adjust the magnitude of the capacitive coupling between theresonators 151 and 156. In other words, the magnitude of the capacitivecoupling between the resonators 151 and 156 is adjustable by adjustingthe number of and distance between the plurality of through hole lines108T constituting the coupling adjustment section 108.

The present embodiment achieves such a characteristic that the insertionloss steeply changes in both of the first passband-vicinity region andthe second passband-vicinity region, and in particular, achieves such acharacteristic that the insertion loss changes more steeply in the firstpassband-vicinity region than in the second passband-vicinity region.

In the present embodiment, the partition 107 is disposed to pass betweenthe resonator conductor portion 1520 and the resonator conductor portion1550. The resonator conductor portion 1520 and the resonator conductorportion 1550 respectively constitute the resonator 152 and the resonator155, which are magnetically coupled to each other although not adjacentto each other in circuit configuration. The magnetic coupling betweenthe resonators 152 and 155 can be weaker than the electromagneticcoupling between any two resonators that are adjacent to each other incircuit configuration. According to the present embodiment, it is thuspossible to establish magnetic coupling between the resonators 152 and155 while disposing the partition 107 to pass between the resonatorconductor portion 1520 and the resonator conductor portion 1550. Thepresent embodiment thus achieves both of prevention of deterioration inthe attenuation characteristic associated with the lowest-orderwaveguide mode by the provision of the partition 107 and the creation ofattenuation poles by establishing magnetic coupling between theresonators 152 and 155. This results in the favorable characteristics ofthe band-pass filter 100.

In the present embodiment, the resonator conductor portions 1510, 1520,1550 and 1560 of the resonators 151, 152, 155 and 156 having theabove-described relationship in circuit configuration are configured tohave the above-described physical relationship. The present embodimentthus realizes the band-pass filter 100 which has two cross couplings andis simple in structure.

Now, an example of characteristics of the band-pass filter 100 accordingto the present embodiment and an example of characteristics of aband-pass filter of a second comparative example will be discussed. Theband-pass filter of the second comparative example has the sameconfiguration as that of the band-pass filter 100 except that thepartition 107 is omitted.

FIG. 25 illustrates an example frequency response of the insertion lossof the band-pass filter 100 according to the present embodiment. FIG. 26illustrates an example frequency response of the insertion loss of theband-pass filter of the second comparative example. The frequencyresponses shown in FIGS. 25 and 26 were obtained by simulation. In FIGS.25 and 26, the horizontal axis represents frequency, and the verticalaxis represents insertion loss. In the examples shown in FIGS. 25 and26, the band-pass filter 100 and the band-pass filter of the secondcomparative example have a passband of approximately 26 to 30 GHz, andthe center frequency of the passband is approximately 28 GHz.

For the band-pass filter 100 used in the simulation, the magnitudes ofthe two cross couplings were adjusted, based on the presence of thepartition 107, so as to obtain such a characteristic that the insertionloss steeply changes in both of the first passband-vicinity region andthe second passband-vicinity region, as shown in FIG. 25. The firstpassband-vicinity region is a frequency region of approximately 24 to 26GHz. The second passband-vicinity region is a frequency region ofapproximately 30 to 32 GHz. Note that the characteristic shown in FIG.25 exhibits no apparent attenuation pole in the second passband-vicinityregion. This is because the capacitive coupling between the resonators151 and 156 caused a slight reduction in the insertion loss at anattenuation pole that was caused to occur in the secondpassband-vicinity region by the magnetic coupling between the resonators152 and 155. Although no apparent attenuation pole is observed in thesecond passband-vicinity region, the characteristic shown in FIG. 25exhibits a steep change in the insertion loss in that region.

The characteristic of the band-pass filter of the second comparativeexample shown in FIG. 26 exhibits a lower insertion loss than that ofthe band-pass filter 100 in both of the first passband-vicinity regionand the second passband-vicinity region. This is because, for theband-pass filter of the second comparative example, the omission of thepartition 107 resulted in a deviation of the magnitude of the magneticcoupling between the resonators 152 and 155 from the adjusted magnitudein the band-pass filter 100.

Further, the characteristic of the band-pass filter of the secondcomparative example shown in FIG. 26 exhibits a peak of an extremereduction in the insertion loss in a frequency region near 50 GHz. Thisis considered to be due to unwanted resonance caused by the lowest-orderwaveguide mode. In the characteristic of the band-pass filter 100 shownin FIG. 25, when compared with the characteristic shown in FIG. 26, thepeak present in the frequency region near 50 GHz is shifted to a higherfrequency and the insertion loss at this peak is higher. Accordingly,the characteristic shown in FIG. 25 is better than the characteristicshown in FIG. 26 in terms of attenuation characteristic in a frequencyregion above the passband.

It is apparent from FIG. 25 that the band-pass filter 100 according tothe present embodiment provides the favorable characteristics achievingsteep changes in the insertion loss in both of the first and secondpassband-vicinity regions and prevention of deterioration in theattenuation characteristic associated with the lowest-order waveguidemode.

The configuration, operation and effects of the present embodiment areotherwise the same as those of the first embodiment.

The present invention is not limited to the foregoing embodiments, andvarious modifications may be made thereto. For example, the number andthe configuration of the resonators are not limited to those illustratedin the foregoing embodiments, and can be freely chosen as far as therequirements of the appended claims are met. Further, at least part ofthe connecting portion of the shield 6 may be composed of conductorlayer(s) formed on one or more side surfaces of the main body 2, insteadof a plurality of through hole lines. Still further, the partition maybe composed of plate-shaped conductor portions, instead of a pluralityof through hole lines.

Obviously, many modifications and variations of the present inventionare possible in the light of the above teachings. Thus, it is to beunderstood that, within the scope of the appended claims and equivalentsthereof, the invention may be practiced in other embodiments than theforegoing most preferable embodiments.

What is claimed is:
 1. A band-pass filter comprising: a main body formedof a dielectric; a first input/output port and a second input/outputport integrated with the main body; five or more resonators providedwithin the main body, located between the first input/output port andthe second input/output port in circuit configuration, and configured sothat capacitive coupling is established between every two of theresonators adjacent to each other in circuit configuration, each of thefive or more resonators including a resonator conductor portion formedof a conductor, the five or more resonators including: a first resonatorand a second resonator that are configured to be magnetically coupled toeach other although not adjacent to each other in circuit configuration;and a third resonator and a fourth resonator that are configured to becapacitively coupled to each other although not adjacent to each otherin circuit configuration; and a notch filter section for attenuating asignal of a predetermined frequency higher than a passband of thehand-pass filter; wherein the first resonator and the third resonatorare adjacent to each other in circuit configuration, the secondresonator and the fourth resonator are adjacent to each other in circuitconfiguration, the resonator conductor portion of the first resonatorand the resonator conductor portion of the second resonator arephysically adjacent to each other without any resonator conductorportion of another resonator therebetween, the resonator conductorportion of the third resonator and the resonator conductor portion ofthe fourth resonator are physically adjacent to each other without anyresonator conductor portion of another resonator therebetween, theresonator conductor portion of the first resonator and the resonatorconductor portion of the third resonator are physically adjacent to eachother without any resonator conductor portion of another resonatortherebetween, and the resonator conductor portion of the secondresonator and the resonator conductor portion of the fourth resonatorare physically adjacent to each other without any resonator conductorportion of another resonator therebetween.
 2. A band-pass filtercomprising: a main body formed of a dielectric; a first input/outputport and a second input/output port integrated with the main body; andfive or more resonators provided within the main body, located betweenthe first input/output port and the second input/output port in circuitconfiguration, and configured so that electromagnetic coupling isestablished between every two of the resonators adjacent to each otherin circuit configuration, each of the five or more resonators includinga resonator conductor portion formed of a conductor, the five or moreresonators including: a first resonator and a second resonator that areconfigured to be magnetically coupled to each other although notadjacent to each other in circuit configuration; and a third resonatorand a fourth resonator that are configured to be capacitively coupled toeach other although not adjacent to each other in circuit configuration,wherein the first resonator and the third resonator are adjacent to eachother in circuit configuration, the second resonator and the fourthresonator are adjacent to each other in circuit configuration, theresonator conductor portion of the first resonator and the resonatorconductor portion of the second resonator are physically adjacent toeach other without any resonator conductor portion of another resonatortherebetween, the resonator conductor portion of the third resonator andthe resonator conductor portion of the fourth resonator are physicallyadjacent to each other without any resonator conductor portion ofanother resonator therebetween, the resonator conductor portion of thefirst resonator and the resonator conductor portion of the thirdresonator are physically adjacent to each other without any resonatorconductor portion of another resonator therebetween, the resonatorconductor portion of the second resonator and the resonator conductorportion of the fourth resonator are physically adjacent to each otherwithout any resonator conductor portion of another resonatortherebetween, and each of the five or more resonators is a resonatorwith open ends.
 3. The band-pass filter according to claim 2, whereinthe five or more resonators are five resonators, the first resonator isa resonator that is the closest to the first input/output port incircuit configuration, the second resonator is a resonator that is theclosest to the second input/output port in circuit configuration, thethird resonator is a resonator that is the second closest to the firstinput/output port in circuit configuration, and the fourth resonator isa resonator that is the second closest to the second input/output portin circuit configuration.
 4. The band-pass filter according to claim 2,wherein the five or more resonators are six resonators, the firstresonator is a resonator that is the second closest to the firstinput/output port in circuit configuration, the second resonator is aresonator that is the second closest to the second input/output port incircuit configuration, the third resonator is a resonator that is theclosest to the first input/output port in circuit configuration, and thefourth resonator is a resonator that is the closest to the secondinput/output port in circuit configuration.
 5. The band-pass filteraccording to claim 2, further comprising a notch filter section forattenuating a signal of a predetermined frequency higher than a passbandof the band-pass filter.
 6. The band-pass filter according to claim 2,wherein the main body includes a multilayer stack composed of aplurality of dielectric layers stacked together.
 7. The band-pass filteraccording to claim 6, wherein the respective resonator conductorportions of the first to fourth resonators are located at the sameposition in the multilayer stack in a direction in which the pluralityof dielectric layers are stacked.
 8. The band-pass filter according toclaim 2, wherein the electromagnetic coupling between every two of theresonators adjacent to each other in circuit configuration is capacitivecoupling.
 9. A band-pass filter comprising: a main body formed of adielectric; a first input/output port and a second input/output portintegrated with the main body; five or more resonators provided withinthe main body, located between the first input/output port and thesecond input/output port in circuit configuration, and configured sothat electromagnetic coupling is established between every two of theresonators adjacent to each other in circuit configuration, each of thefive or more resonators including a resonator conductor portion formedof a conductor, the five or more resonators including: a first resonatorand a second resonator that are configured to be magnetically coupled toeach other although not adjacent to each other in circuit configuration;and a third resonator and a fourth resonator that are configured to becapacitively coupled to each other although not adjacent to each otherin circuit configuration; a shield formed of a conductor and integratedwith the main body, the shield including a first portion and a secondportion spaced from each other in a first direction, and a connectingportion connecting the first and second portions, the first portion, thesecond portion and the connecting portion being arranged to surround thefive or more resonators; and a partition formed of a conductor, providedwithin the main body, and electrically connected to the shield, whereinthe first resonator and the third resonator are adjacent to each otherin circuit configuration, the second resonator and the fourth resonatorare adjacent to each other in circuit configuration, the resonatorconductor portion of the first resonator and the resonator conductorportion of the second resonator are physically adjacent to each otherwithout any resonator conductor portion of another resonatortherebetween, the resonator conductor portion of the third resonator andthe resonator conductor portion of the fourth resonator are physicallyadjacent to each other without any resonator conductor portion ofanother resonator therebetween, the resonator conductor portion of thefirst resonator and the resonator conductor portion of the thirdresonator are physically adjacent to each other without any resonatorconductor portion of another resonator therebetween, the resonatorconductor portion of the second resonator and the resonator conductorportion of the fourth resonator are physically adjacent to each otherwithout any resonator conductor portion of another resonatortherebetween, the resonator conductor portion of each of the five ormore resonators extends in a direction intersecting the first direction,the partition is in contact with the first portion and the secondportion, and at least part of the partition extends to pass between theresonator conductor portion of the first resonator and the resonatorconductor portion of the second resonator.
 10. The band-pass filteraccording to claim 9, wherein the main body includes a multilayer stackcomposed of a plurality of dielectric layers stacked together in thefirst direction.
 11. The band-pass filter according to claim 10, whereinthe multilayer stack includes a main portion composed of two or moredielectric layers stacked together, among the plurality of dielectriclayers, the main portion has a first end face and a second end facelocated at opposite ends in the first direction, the first portion isformed of a first conductor layer disposed on the first end face, thesecond portion is formed of a second conductor layer disposed on thesecond end face, and the partition runs through the two or moredielectric layers.
 12. The band-pass filter according to claim 11,wherein the partition includes a plurality of first through hole lineseach running through the two or more dielectric layers, and each of theplurality of first through hole lines includes two or more through holesconnected in series.
 13. The band-pass filter according to claim 11,wherein the connecting portion of the shield includes a plurality ofsecond through hole lines each running through the two or moredielectric layers, and each of the plurality of second through holelines includes two or more through holes connected in series.
 14. Aband-pass filter comprising: a main body formed of a dielectric; a firstinput/output port and a second input/output port integrated with themain body; and five resonators provided within the main body, locatedbetween the first input/output port and the second input/output port incircuit configuration, and configured so that electromagnetic couplingis established between every two of the resonators adjacent to eachother in circuit configuration, each of the five resonators including aresonator conductor portion formed of a conductor, the five resonatorsincluding: a first resonator and a second resonator that are configuredto be magnetically coupled to each other although not adjacent to eachother in circuit configuration; and a third resonator and a fourthresonator that are configured to be capacitively coupled to each otheralthough not adjacent to each other in circuit configuration, whereinthe first resonator and the third resonator are adjacent to each otherin circuit configuration, the second resonator and the fourth resonatorare adjacent to each other in circuit configuration, the resonatorconductor portion of the first resonator and the resonator conductorportion of the second resonator are physically adjacent to each otherwithout any resonator conductor portion of another resonatortherebetween, the resonator conductor portion of the third resonator andthe resonator conductor portion of the fourth resonator are physicallyadjacent to each other without any resonator conductor portion ofanother resonator therebetween, the resonator conductor portion of thefirst resonator and the resonator conductor portion of the thirdresonator are physically adjacent to each other without any resonatorconductor portion of another resonator therebetween, the resonatorconductor portion of the second resonator and the resonator conductorportion of the fourth resonator are physically adjacent to each otherwithout any resonator conductor portion of another resonatortherebetween, the first resonator is a resonator that is the closest tothe first input/output port in circuit configuration, the secondresonator is a resonator that is the closest to the second input/outputport in circuit configuration, the third resonator is a resonator thatis the second closest to the first input/output port in circuitconfiguration, and the fourth resonator is a resonator that is thesecond closest to the second input/output port in circuit configuration.15. The band-pass filter according to claim 14, wherein theelectromagnetic coupling between every two of the resonators adjacent toeach other in circuit configuration is capacitive coupling.
 16. Aband-pass filter comprising: a main body formed of a dielectric; a firstinput/output port and a second input/output port integrated with themain body; and six resonators provided within the main body, locatedbetween the first input/output port and the second input/output port incircuit configuration, and configured so that electromagnetic couplingis established between every two of the resonators adjacent to eachother in circuit configuration, each of the six resonators including aresonator conductor portion formed of a conductor, the six resonatorsincluding: a first resonator and a second resonator that are configuredto be magnetically coupled to each other although not adjacent to eachother in circuit configuration; and a third resonator and a fourthresonator that are configured to be capacitively coupled to each otheralthough not adjacent to each other in circuit configuration, whereinthe first resonator and the third resonator are adjacent to each otherin circuit configuration, the second resonator and the fourth resonatorare adjacent to each other in circuit configuration, the resonatorconductor portion of the first resonator and the resonator conductorportion of the second resonator are physically adjacent to each otherwithout any resonator conductor portion of another resonatortherebetween, the resonator conductor portion of the third resonator andthe resonator conductor portion of the fourth resonator are physicallyadjacent to each other without any resonator conductor portion ofanother resonator therebetween, the resonator conductor portion of thefirst resonator and the resonator conductor portion of the thirdresonator are physically adjacent to each other without any resonatorconductor portion of another resonator therebetween, the resonatorconductor portion of the second resonator and the resonator conductorportion of the fourth resonator are physically adjacent to each otherwithout any resonator conductor portion of another resonatortherebetween, the first resonator is a resonator that is the secondclosest to the first input/output port in circuit configuration, thesecond resonator is a resonator that is the second closest to the secondinput/output port in circuit configuration, the third resonator is aresonator that is the closest to the first input/output port in circuitconfiguration, and the fourth resonator is a resonator that is theclosest to the second input/output port in circuit configuration. 17.The band-pass filter according to claim 16, wherein the electromagneticcoupling between every two of the resonators adjacent to each other incircuit configuration is capacitive coupling.